Hello.
I need some advice about keeping kite stable unhook with one hand. Particularly, I am trying to do ralley with simple grab with back hand. But as soon as I release my back hand in the air , kite quickly goes into downloop because I pull with my front hand. It didn't do actual downloop, but I have no time to take grab and should quickly put my backhand back on bar to catch kite near water. I tried several times but have no any ideas how to help myself and what am I doing wrong. How should I prevent this in theory at least?

This one-hand issue makes me scary to try ralley to blind. I can do pretty stable surface-pass, but I guess it works because when I do it I have slacked lines (go under the kite before passing). If I am trying to do it with powered kite and without slack lines than same issue appears: kite goes into downloop.

I am riding RPM 12/9. I keep my front hand in the middle of the bar with depower rope between middle and index fingers. Would be glad any help. Thank you.

I always thought the Indy glide to blind looked sick and I remember seeing videos of Andre Phillip, Aaron Hadlow and Keahi De Aboitiz pulling them off.

As for your one-handed-railey, I would definatelly start with your 12m kite as this one turns slower.
Consider using a slower turning speed setup on the steering lines (change knot) during a session where you only focus on that particular trick.Keep your arms bend (90degrees) and just in front of your face. This will help you later on your railey's to blind and other handle passes as it reduces the distance towards your hip.

I would also encourage you to:
A) practice the one handed movement on dry, with your kite at 45degree, trying to build up the muscle memory in your hand, arm and shoulders.
B) Put up a control bar on a tree of solid point practice dangeling one handed and passes in general.

Further I read that you feel comfortable with the surface pass, nice one!
You should be able to do them in both directions AND frontside/ backside ASWELL as popping into blind (backside 180) or into wrapped (frontside 360). Once you get a hang of them, they are a lot of fun and you can combine them with kickers.

After this you can look at your railey's to blind and progress them into one handed railey's to blind.
You see, every step along the way is key, if you understand that you can work your way through it.

On a last note, I'm going to try the one handed railey's to blind today for you and give you some feedback afterwards.

Been out in stormy 10-25knots on the 10m and tried the one handed railey/ one handed railey to blind (grab).

I’ve approached the trick as following;
-Riding in with good speed, as if you were attempting a standard railey (not too slow).
-Index and middle finger of your front hand crossing over the depower strap.
-Index finger of your backhand touching your depower strap.
-As you ride in try to slowly let go with you backhand and observe if your kite position changes!
-Put your backhand back on and re-adjust your kite and adjust your fronthand placement and pressure.
-Repeat this process over and over while you ride in until your kite remains in a stable position.
-It’s all about your front hand position, hand pressure and awareness of what you are doing.
-unhook, edge, flick all done 2 handed, let go with your back hand on the way to the apex and go for an easy grab.
-If you are able to do railey’s to blind you can try to do the backside 180 after you feel comfortable with the one handed flying sensation.